1. Field of the Invention
This invention relates to a device for transmitting an RF signal which is capable of being received at a remote location and, more specifically, to such a device which is self-contained and installed on a vehicle power transmission device to indicate when a predetermined parameter associated with the operation of the power transmission device is exceeded.
2. Description of the Prior Art
As heavy duty trucks become more expensive and more complicated, there remains a need for providing systems which are capable of monitoring the various operating parameters of such trucks to insure that they will not be operated under conditions which are likely to damage or destroy any of their components. Although electronic signal and sensing devices are more commonly being utilized, they are usually employed in onboard electrical systems where the existence of some problems would only be indicated to the driver of the vehicle. For example, U.S. Pat. No. 4,229,728 is directed to a tire pressure monitoring system which includes at each wheel a self-contained tire monitor which is capable of transmitting a signal to the operator when the air pressure in one of the tires is at a low condition. While such a system as disclosed in U.S. Pat. No. 4,229,728 might be satisfactory for its limited purposes, the system is directed to only one operating parameter which is essential for proper truck operation and is sufficiently expensive and complicated to place its overall value in doubt.
Additionally, in organizations which operate an entire fleet of such heavy duty trucks, there is a continuing need for insuring that all such trucks are in a proper operating condition prior to their being dispatched from a central location. As a result, there is a continuing interest in providing a system which could also facilitate rapid, inexpensive and reliable monitoring of various parameters for each of the heavy duty trucks prior to its being released for operation on the highways.